This invention relates to surgical stapling instruments, and more particularly to surgical stapling instruments in which the stapling is performed between two opposing legs of a substantially rigid frame.
Among the known surgical stapling instruments are those which include a substantially rigid frame having two opposing legs with a staple crimping anvil mounted on one leg and a staple carrying assembly and actuator mechanism mounted relatively to the other leg. One example of such an instrument is shown in Strekopitov et al. U.S. Pat. No. 3,080,564. Typically in such instruments, the two opposing legs are part of a U-shaped portion of the frame. In order to use the instrument, the staple carrying assembly is retracted and the U-shaped portion of the frame is placed around the tissue to be stapled. The staple carrying assembly is then advanced toward the anvil by operation of the actuator mechanism to clamp the tissue between the staple carrying assembly and the anvil. Thereafter, the actuator mechanism is further operated to cause the staples to be driven from the staple carrying assembly, through the tissue, and against the anvil, thereby crimping the staples and stapling the tissue. The instrument is removed from the stapled tissue by retracting the now-empty staple carrying assembly to release the clamping of the tissue.
During use of instruments of the type described above, considerable force is exerted on the frame of the instrument in a manner which tends to drive the opposing legs of the frame apart. All of the forces required to clamp the tissue and to drive and crimp the staples cumulate so that the maximum force tending to separate the legs of the frame can be very high. Depending on the size of the instrument, the number of staples, and the kind of tissue involved, this force may be several hundred pounds in known instruments and in known applications of those instruments.
The frame-distorting forces described above can have deleterious effects on the performance of the instrument. Particularly if the staple carrying assembly and anvil are mounted relative to respective opposite legs of the frame, distortion of the frame can cause misalignment of the anvil and the staple carrying assembly so that the staples do not enter the anvil pockets properly and therefore are not properly crimped. The anvil and the staple carrying assembly may also not remain parallel to one another so that some staples (especially those near the open end of the U-shaped portion of the frame) may not reach the anvil sufficiently for complete crimping.
In order to eliminate or ameliorate these problems, some instruments of this type have been provided with alignment and/or clamping means adjacent the normally open side of the U-shaped portion of the frame. In Green et al. U.S. Pat. No. 3,494,533, for example, a threaded pin is mounted adjacent the normally open side of the frame so that after the instrument is in position on the tissue, the pin can be extended across the open side of the frame and threaded into the opposite frame leg to clamp the frame legs together. This prevents the legs of the frame from spreading apart during subsequent tissue clamping and staple driving.
The use of frame reinforcement of the type described above produces good results, but it also adds several steps to the operation of the instrument and may increase the number of hands required to operate the instrument.
The problems associated with frame distortion are particularly aggravated in large instruments which are required to drive a large number of staples simultaneously. For example, there is increasing interest in using large instruments of this type for placing one or more rows of staples transversely across a major portion of the stomach in a procedure known as gastric bypass. One of the purposes for which this procedure is used is to reduce the effective size of the stomach and thereby reduce the intake of food by individuals who are extremely obese (a condition known as morbid obesity). The instruments sometimes used for performing this procedure simultaneously drive approximately 30 staples in an array of two parallel rows approximately 90 mm in length. Because of the considerable span of the instrument and the large forces involved, the problems associated with distortion of the frame of the instrument can be particularly severe in this procedure.
In some procedures there is interest in applying more staples than can be applied at one time by any of the presently available surgical stapling instruments. In the gastric bypass procedure mentioned above, for example, there have been occasional reports that a double row of staples may not be sufficient in some cases. The stress on the staple line may be so great that the staples tear away, thereby allowing the stomach to return to its original size. Additional staples would therefore be desirable to increase the strength of the staple line and reduce the risk of staples tearing out. Although additional staples can be applied by multiple use of the available instruments, it would be preferable to have an instrument which was capable of applying more staples in a single operation. Increasing the number of staples driven, however, further increases the forces which the instrument must be able to apply and withstand, and makes frame distortion an even more serious problem.
In view of the foregoing it is an object of this invention to improve and simplify surgical stapling instruments of the type in which tissue is stapled between the two opposing legs of the instrument frame.
It is a more particular object of this invention to provide surgical stapling instruments of the type mentioned above in which the frame is automatically reinforced in the vicinity of the two opposing legs during actuation of the instrument.
It is another more particular object of the invention to provide surgical stapling instruments of the type described above which are capable of simultaneously applying substantially more staples than is possible with the presently available instruments, while at the same time substantially reducing or preventing distortion of the frame in the vicinity of the two opposing legs.